Line-contact transistor



June 9, 1953 J. 1. PANTCHECHNIKOFF "2,641,633

LINE-CONTACT TRANSISTOR Filed March 27', .1952

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ATTORNEY Patented June 9, 1953 LINE-CONTACT TRAN SISTOR V Jacques I. Pantehechnikoff, Princeton, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application March 27, 1952, Serial No. 278,805

7 Claims.

This invention relates generally to semi-conductor devices suitable for use in amplifier and the like circuits, and more particularly relates to a transistor of the type having line contact electrodes.

In applicants copending application, Serial No. 84,672, filed March 31, 1949, entitled Semi- Conductor Devices and assigned to the assignee of this application, there has been disclosed a semi-conductor device or transistor provided with a pair of line contact electrodes. These line contact electrodes may be used as the emitter and collector electrodes of the device respectively, while a third electrode, the base electrode, is in low-resistance contact with the semiconducting body. The provision of line contact electrodes improves the geometry of the device and thereby the electric field configuration so that a larger portion of the injected charge carriers, which may be ,holes or electrons, can be collected. Preferably, the line contact electrodes consist each of a wire or filamentary conductor which is pressed into intimate contact with the semi-conducting body or crystal.

U. S. Patent 2,580,027, granted on December 25, 1951, to H. Johnson and assigned to the assigneeof this application discloses an improved line contact transistor. The Johnson transistor comprises two semi-conducting bodies between which are provided two filamentary conductors or fine metallic wires which provide the emitter and collector electrodes. A separate base electrode may be in low-resistance contact with each of the bodies. Such-a device represents a single amplifier device having alarger current carrying capacity because the currents flowing between emitter and collector may pass through either one of the two semi-conducting bodies. In a-ccordancewith the present invention, the Johnson line contact transistor is modified so as to provide a device which may be used as a twostage amplifier.

It is accordingly an objectjof the present invention to provide an improved line contact transistor device.

A further object of the invention is to provide an. improved transistor device of the line contact type which is adapted to provide a twin amplifier device suitable, for example, in twostage amplifier or push-pull amplifier circuits.

The. line. contact. transistor device of the present invention. comprises two bodies of semiconducting. material having two surfaces facmg: each other. A first filamentary conductor which may form the emitter is-in rectifiyingcontact with the surfaces of both bodies. A further pair of filamentary conductorsmay form two individual collector electrodes and each. con ductor is in contact with only. one surface of the two bodies- It is, of course, feasible to make the first conductor the collector and the pair of conductors individual emitters of the device. These three conductors are disposed substantially parallel and closely adjacent to each other. A base electrode is provided in low-resistance contact with each of the two bodies. Means ar'e provided for causing an intimate contactbetween the first conductor and both of thebodies' and between the pair of conductors and their associated bodies. The resulting transistor device accordingly has a single emitter electrode, two collectors and two base electrodes.

The novel features that are considered characteristic of this invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization'and method of operation, as well as additional objects and advantages-thereof, will best be understood vfrom the following description when read in connection with the accompanying drawing, in which: I

Figure 1 is a cross-sectional view of a transister device embodying the present inven'tior'i; Figure 21s a sectional view of the device of Figure 1 taken on line 2 -2 of Figure 1; I

Figure 3 is a side el evational view of a preferred modification of the transistor device in accordance with the invention; 7

Figure '4 is a sectional view of the device of Figure 3 taken on line 44 of Figure 3;

Figure 5' is a circuit diagram of a push-pull amplifier circuit including the transistor device of the invention; and 1 Figure 6 is a circuit diagram of a two-stage amplifier circuit utilizing the device of the" invention.

Referring now to the drawing in which like components'are designated by the same reference numerals throughout thefigures and particularly to Figures 1 and 2 there is illustrated a transistor device comprising a body or block illof semi-conducting material. Block itmay, for example, consist'of silicon or preferably of germanium' which may be of the N type now well known in the art. A second block I l of the same material as block" I 6' is provided. The two blocks each other.

A central filamentary conductor I4 such as a fine metallic wire is disposed between the plane surfaces I2 and I3 of blocks I and II. As clearly shown in Figure 1, wire I4 is in contact with both surfaces I2 and I3. A further pair of filamentary conductors I and I6 is provided between the blocks I0 and II. Conductors I5 and I6 may also consist of fine metallic wires and are disposed substantially parallel to wire I4 and closely adjacent to each other. As clearly shown in Figure 1, wire I5 is in contact only with the surface I2 of the block III, while wire I6 is in contact only with the surface I3 of the block I The central wire I4 may form the emitter electrode which is common to both the blocks IB and II, while the wires I5 and I6 may form individual collector electrodes. However, wire I4 may also form the collector in which case wires 5 and I6 provide two emitters.

Wire I4 has a diameter which is larger than that of the wires I5 and I6. Wires I5 and I6 are maintained in intimate contact with their respective surfaces I2 and I3 by means of insulating strips I? and I8 which have such thickness that the wires I5 and I6 will be pressed into contact with their respective surfaces I2 and I3 when the central wire I4 is in contact with both of these surfaces.

A suitable slab of metal 2|! is in low-resistance or ohmic contact with the body III. A similar slab of metal 2| is in low-resistance contact with the body The metallic slabs 29 and 2| form two base electrodes in contact with their respective bodies Ill and I The line contact electrodes or wires I4, I5, I6 are mechanically pressed against the surfaces I2 and I3. This may be effected by pressing the slabs 20 and 2| against each other as indicated schematically in Figure l by the arrows 22 and 23. This mechanical pressure will insure intimate contact between wire I4 and the surfaces I2 and I3 of the blocks I0 and I I, between the wire I5 and the surface I2 and finally bet-ween the wire I6 and the surface I3. Thus intimate substantially line contact between the major portion of the length of each of the wires I4, I5 and I6 and its assosociated body or bodies is provided.

It will be understood that surfaces I2 and I3 may be ground or polished and etched as is conventional. Wires I4, I5 and-|6 may consist, for example, of tungsten-nickel, beryllium, copper or Phosphor bronze. consist of a metal which is softer than the blocks ID and. ||.v Thus, if blocks II! and II consist of germanium which is a comparatively hard material, the central wire |4 may, for example, consist of tungsten and may have a diameter of two mils. The wires I5 and E6 may consist of Phosphor bronze and may have a diameter of one mil. In that case, the insulating strips I3 may consist of mica sheets having a thickness of one mil. The spacing between the central wire I4 and wires I 5 and I 6 should be equal and may amount, for example, to two mils. However, it is to be understood that the spacing between wire I 4 and I5 on the one hand or wire I6 on the other hand may be considerably larger than two mils.

Thus, the wire I4 may form a common emitter electrode for the two amplifier devices, each of which comprises a collector electrode formed by either wire |5 or I6 and a base electrode provided by metallic slab 2| or 2 I.

Referring now to Figures 3 and 4, there is illustrated a preferred modification of the line contact transistor of the invention. The device Preferably, the wires |4|6.

again consists of two blocks I0 and II of semiconducting material having substantially parallel surfaces I2 and I3 respectively, The central wire I4 is in line contact with both surfaces I2 and I3, while the wire I5 is in contact with surface I2 and the wire I6 is in contact with surface I3. The insulating strips I1 and I3 respectively insulate the wires 15 and I6 from the surfaces I3 and I2. The metallic slab 2| forms a base electrode for the block I I.

The base electrode for the block I0 may be provided by a metallic foil 25 which may, for example, consist of copper and which may enclose a pad 26 of yieldable material such as rubber. A metallic sheet 21 which may, for example, consist of brass is in electric contact with the copper foil 25. Wires 30 and 3| are in electric contact with the metallic slab 2I and with the metallic sheet 2'! respectively, thereby to provide an electrical connection to the two base electrodes. As clearly shown in Figure 3, the wires I4, I5 and I6 may extend from the plastic housing 32 which encloses the device of the invention. A cover 33 also consisting of a plastic insulating material may have a press fit with the housing 32 so as to provide the desired contact pressure between the line contact electrodes |5|'| and their associated bodies when the cover 33 is pressed into the housing. 32. The rubber pad 26 will distribute the pressure exerted by cover 33 so as to press each of the wires I5, I6, I! with a uniform pressure against their associated bodies.

Referring now to Figure 5 there is illustrated a push-pull amplifier circuit which makes use of the transistor device of the invention. The device of the invention has been shown'schematically in Figure 5. One of the transistor devices includes the body I0, emitter electrode I4a, collector electrode I5 and the base 20, while the other device comprises the body emitter I4b, collector I6 and base 2|. The two emitters I40, and |4 b are, of course, identical as shown in Figures 1-4. A push-pull input signal, which should be balanced with respect to ground, is impressed on the input terminals 35 which are coupled through coupling capacitors 36, 31 to the two base electrodes 20, 2|. The emitter electrodes Ma and MI) are grounded as shown and are con-' nected to the bases 20, 2| through impedance elements such as resistors 40, 4|.

The output signal is derived from the two collectors I5, I6 and may be obtained from output terminals 42 which are coupled to the collectors through coupling capacitors 43, 44. The output load resistors 45 and 46 are connected individually between the two collectors I5, I6 and a source of bias voltage such as battery 41, which may be bypassed for signal frequency currents by capacitor 48. Battery 41 has its positive terminal grounded while its negative terminal is connected to the junction point of the two load resistors 45, 46. The required emitter bias voltage may be developed across the resistors 4|] and 4| as is conventional.

The circuit of Figure 5 is conventional and an amplified push-pull signal is derived from the output terminals 42, which is an amplified replica of the input signal.

The device of the invention may also be utilized in a two-stage amplifier circuit of the type illustrated in Figure 6; The amplifier circuit of Figure 6 has been disclosed and claimed in a copending application to W. M. Webster, Jr., Serial No. 72,152, filed on January 22, 1949, and assigned to the assignee of this application, now

accness Patent No.- 2,595,496. An input. signal to: be amplified maybe impressed on input terminalsgrounded while the input signal developed across.

inductor 54 is-impressed'on the emitter lab. The mp ified output signal is developed across in..- ductor 55 connected between battery 4'! and col.- lector l5. Accordingly, the second amplifier stage is a grounded base transistor having emitter input and collector output. The amplified output signal may be obtained from output coil 5'! inductively coupled to coil 55, and the output signal may be obtained from output terminals 58. It is believed that the operation of the two-stage amplifier of Figure 6 will be evident from the above description.

If wire I4 forms the common collector while wires I5 and i6 represent two separate emitter electrodes, the. device of the invention may be used to add two input signals. lhe two input signals are individually impressed on the two emitters and an amplified output signal representative of the added input signals is derived from the collector.

There has thus been disclosed a transistor device of the line contact type which provides two amplifiers having a common emitter electrode. A device of this type may, for example, be used in a push-pull or in a two-stage amplifier circuit. The device of the invention has a larger current carrying capacity than that of a conventional transistor device having point contact electrodes.

What is claimed is:

l. A transistor device comprising two bodies of semi-conducting material, each having a discrete surface area, a first filamentary conductor providing a first electrode in contact with both of said surface areas, a second filamentary conductor providing a second electrode in contact with only one of said surface areas, a third fila mentary conductor providing a third electrode in contact with only the other one of said surface areas, said conductors being disposed substantially parallel and closely adjacent to each other, an additional electrode in low-resistance contact with another surface area of each of said bodies, and means for providing and maintaining intimate contact between said conductors and the respective surface areas of said bodies.

'2. A transistor device comprising two bodies of semi-conducting material, each having a surface area, said surface areas facing each other and extending substantially parallel to each other, a first filamentary conductor providing a first electrode in contact with both of said surface areas, a second filamentary conductor providing a second electrode in contact with one of said surface areas, a third filamentary conductor providing a third electrode in contact with only the other one of said surface areas, said conductors consisting of metal and being disposed substantially parallel and closely adjacent to each other, an additional electrode in low-resistance contact with another surface areaof each of said bodies, and means for providing and maintaining intimate contact be- 6 tween said conductors and the respective surface:- areas ofsaid-bodies.

3. A transistor device comprisingtwo bodies of semi-conductingmaterial, each-having a substantially plane surface, said surfaces facing eachother, a first fine metallic wire forming a first electrode and in contact with both of said surfaces, a second fine metallic wire forming a second electrode and in contact with one of" said: surfaces, a third fine metallic wire forming a third electrode and in contact with the other one of' said surfaces, said wires being disposed substantially parallel and closely adjacent to eachother, an additional electrode in low-resistance contact with another, surface area of each of said bodies, and means for providing and maintaininginti'mate contact" between said first wire and. both of said bodies and between said second and third" wires and their associated body.

4. A transistor device adapted for use as a twostage amplifier or the like and comprising a first 1 and a third filamentary conductor, each having a diameter less than that of said first conductor, said second conductor being in contactwith the flat surface of said first body only and providing a first collector electrode, said third conductor being in contact with the flat surface of said secand body only and'providing a second collector electrode, said conductors being disposed sub--. stantially parallel and closely adjacent to each other, a pair of base electrodes, each being in lowresistance contact with one of said bodies, and j means for pressing said first conductor against both of said bodies and said second and thirdcom ductors against said first and second body respectively to provide intimate substantially line contact between themajor portion of the length of each of said conductors and its associated body.

or bodies.

5. A transistor device adapted for use as a twostage amplifier or the like and comprising a first and a second body of semi-conducting material,

each having a substantially fiat surface, said surelectrode, a second and a third fine wire, each having a diameter less than that of said first wire. said second wire being in contact with the fiat surface of said first body and providing a first collector electrode, said third wire being in contact with the fiat surface of said second body and providing a second collector electrode, said wires consisting of metal and being disposed substantially parallel and closely adjacent to each other, a pair of base electrodes, each being in low-resistance contact with one of said bodies, and means for pressing said first wire against both of said bodies and said second and third wires against said first and second body respectively to provide intimate substantially line contact between the major portion of the length of each of said wire and its associated body or bodies.

. 6. A device as definedin claim 5 wherein said bodies consist of germanium and wherein said wires consist of a metal substantially softer than germanium.

. 7. A transistor device adapted for use as a twostage amplifier or the like and comprising a first and a second body of semi-conducting material,

each having a substantially fiat surface, said surfaces facing each other, a first filamentary conductor provided between said surfaces and in contact with both of said surfaces, said first conductor providing an emitter electrode, a second and a third filamentary conductor, each having a diameter less than that of said first conductor, a first member of insulating material disposed With said second conductor between said bodies so that said second conductor is in contact with the fiat surface of said first body to provide a first collector electrode, a second member of insulating material disposed with said third conductor between said bodies so that said third conductor is in contact with the flat surface of said second body to provide a second collector electrode, said conductors being disposed substantially parallel and closely adjacent to each other, and a pair of base electrodes, each being in low-resistance con-' tact with one of said bodies, said members having a thickness such that said second and third conductors are pressed against said firstand second body respectively when said first conductor is pressed against both of said bodies to provide intimate substantially line contact between the major portion of the length of each of said conductors and its associated body or bodies.

JACQUES I. PANTCHECHNIKOFF.

References Cited ,in the file of this patent UNITED STATES PATENTS Webster May 6, 1952 

